Plugging computer sensors into factories, cars, shops and offices to help them operate more smartly on the industrial Internet, or so-called Internet of Things (IoT), is moving beyond prototypes into the mass market, IBM said on Monday. The computer services and software company, which has struggled with flagging growth in its traditional business in recent years, said its industrial Internet business has surged to 6,000 paying customers from 4,000 at the end of 2015. The IoT, which gives many billions of machine parts the capability to send and receive data, is vital to IBM's turnaround as it has refocused on areas that promise profitable growth such as analytics, security and cloud services.